It's already backed up by specific beats general. If I'm wearing red dragonscale armor which grants resistance to fire, it doesn't matter if my character has a vulnerable to fire trait, the armor over-rides that because it's magical armor. Much the same as a character with 6 strength is incredibly strong while wearing a belt of giant strength. Acknowledging that magic items over-ride general character statistics, and then ignoring a racial/archetype vulnerability is blatantly ignoring the basic rules of the game.

Specific beats general when there's a conflict between two rules. But there's no conflict between a character having resistance and vulnerability towards the same damage type, and indeed, the wording of the rule does provide for this by establishing the order in which resistance and vulnerability are applied. So the whole specific vs general point is moot.

And specific still and always will beat general. If OP had stated that his vulnerabiltiy and resistance were from the same source, this wouldn't be my answer. But OP stated he is vulnerable, and an item is granting resistance. That's very specific. Much like the general rule for AC is 10 + Dex, except where specifically over-ridden by specific things like spells, archetypes or items.

@Lino It's not specific in slightest. "OP stated he is vulnerable" meaning "OP is not resistant" is your own invention that I cannot find a rule citation for. You're arguing based on a specific rule that doesn't exist.

What are you talking about? Where did I ever say that?

@Lino "But OP stated he is vulnerable, and an item is granting resistance." Your answer says this is a clash where the more specific rule prevails. I only see it being a clash if you make the unsupported assumption I laid out in my previous comment, that resistance and vulnerability cannot exist at the same time.

How do you figure that's unsupported? If I'm vulnerable to fire, but I get Protection from Energy cast on me, I'm now resistant to it. I don't suffer from the vulnerability because that's a general rule, whereas the spell is a specific one. How is that ANY DIFFERENT for an item?

@Lino Protection from energy doesn't say anything about removing vulnerability. This is why I say your assumptions are unsupported - you're saying stuff that's not in the books.

For the record, I would agree with you if the resistance/vulnerability rules specifically said one supercedes the other, or if we were discussing an item that specifically said it negates resistance/vulnerability while providing the opposite... but in the general case, nay - resistance and vulnerability can coexist just fine and are covered by the rules as in Szega's answer.

All your examples so far are based on you implicitly reading "you are resistant to X" as including "you are not vulnerable to X" and vice versa - that's the problem

Are we on the same page now?